The present invention concerns a press for the reduction of organic material to flake form for use as a fuel as such or in other processed forms.
A by-product of various wood product operations are wood particles of random shape and size including bark, termed hog fuel in the trade. Such material is a low cost source of energy and is often used to fire industrial boilers. A drawback to such use is its high moisture content prohibiting or severely reducing its utility as a boiler fuel. A USDA report dated 1976, "The Feasability of Utilizing Forest Residues for Energy and Chemicals" noted that when moisture content is 50% of wood particle weight, boiler efficiency is only 65%. When particle moisture content reaches 68% of particle weight, the fuel will not maintain a fire in most boilers. In view of this, while wood waste is readily available such is not a popular source of fuel. A reduction in water content would greatly enhance wood waste as a fuel but the amount of energy necessary to accomplish even partial drying, under known systems, is prohibitive. Drying of wood waste particles by the conventional application of direct heat utilizes upwards of 1200 BTU's per pound of water removed. Accordingly, a potentially usable and readily available fuel is largely unused.
A report appearing in the FOREST PRODUCTS JOURNAL, Volume 31, No. 8, entitled "Potential For Compression Drying of Green Wood Chip Fuel", by John G. Haygreen, discusses the problems of reducing moisture in wood bark and chips by use of mechanical pressure and specifically the use of roll presses, among other equipment, for moisture reduction. Problem areas are mentioned which include the drawing off of expelled water prior to termination of pressing forces to prevent re-absorption of the expelled water. Additionally noted was the fact that high nip pressures in the range of 8,000 to 10,000 pounds per lineal inch minimized the capability of the wood chip to thereafter assume its original water-absorbing form.
The use of a "roller mill" is disclosed in U.S. Pat. No. 2,828,081 for the treating of tree bark for the separation of its cork constituent. The mill performs essentially a separation by a shearing action. U.S. Pat. No. 2,987,988 discloses grooved rolls in a roll mill for the expulsion of moisture from fibrous organic material as does U.S. Pat. No. 1,321,956. None of the known prior art is highly adaptable to present purposes.